The opening of an Economist report about H7N9, a scary new strain of avian flu that has yet to display the capacity for spreading from human to human:

“WU LIANGLIANG went to hospital on March 1st with a tickly cough. After a number of hours hooked up to a saline drip, the 27-year-old pork butcher went home. When he still felt poorly a few days later Mr Wu returned to hospital and was diagnosed with a pulmonary infection. But then instead of recovering, as was expected for a man his age, Wu’s condition worsened rapidly. On March 10th, he became the second person known to have been killed by H7N9, a novel strain of avian flu not previously seen in humans. 

There are now nine identified human cases of H7N9 in the Yangzi delta region, which includes Shanghai, three of which have been fatal. The most recent death reported, announced on April 3rd, was a 38-year-old chef, surnamed Hong, who died in late March. Mr Hong worked in Jiangsu, the province next to Shanghai where four of the other people who contracted H7N9 live (a nearly real-time map endeavours to track the cases). The remaining cases are all in critical condition, but in general they have not deteriorated as swiftly as Mr Wu did. A 35-year-old woman in Anhui province is still alive 22 days after she first became ill.

Many questions surround H7N9’s origin, pattern of infection and treatment (there is no vaccine). Early analyses of the genetic sequence of the virus, which the Chinese authorities have shared with the world, suggest that a familiar strain of avian flu has mutated. Previously infectious only to birds, H7N9 appears now to be able to bind with mammalian cells, making it possible to jump from chickens to animals such as pigs. The World Health Organization (WHO) maintains that that there is no evidence of ongoing human-to-human transmission. If the virus were well adapted to jump between humans, the thinking goes, clearer evidence of transmission would already have emerged among the victims’ close contacts.”